Duct tape is handy for all sorts of things, but it's also good for removing a stuck and stubborn light bulb from its fixture without damaging or breaking the bulb or the socket in the process.
After turning off the light and letting the bulb cool, tear off a long strip of duct tape, and then attach the ends so it's a long closed loop with the adhesive on the inside. Then, holding either end of the loop, place the loop over the light bulb, and attach the tape to the bulb in the centre of the loop. Then flatten the sides of the loop inward until you have duct tape around the bulb and long handles of tape away from each side.
Now that you have the two tape handles, grab the far ends with your fingertips and twist the tape counterclockwise. The torque you get from twisting on the ends of the tape should quickly free the bulb from its socket, all without breaking the bulb.
If the bulb does break, you can always use the old potato trick (jam an unpeeled potato into the socket and twist) to remove the broken bulb from the socket. Check out the video at Real Simple for a visual demonstration.